Getter and method of applying the same



- nullify the effect of this obscuring deposit.-

Patented May 3,1927.

ENHTED STATES PATENT OFFIOE.

DUNCAN MAORAE, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTINGHOUSE LAMP COMPANY, A CORPORATION OF PENNSYLVANIA.

\ GETTER AND METHOD OF APPLYING THE SAME.

No Drawing.

This invention relates to electrical devices such as electron tubes and incandescent electric lamps, and has special reference tomeans for improving the quality thereof.

An object of this invention is the provision of a method of introducing desirable materials into electrical devices of the above character without the simultaneous introduction of substances deleterious to the same.

Another object of the present invention is the provision of simple and improved means for maintaining the candle power and increasing the efiicienc of incandescent lamps.

Other objects of t is invention will be ap- 7 parent from a reading of the following specification.

While the present invention has many applicationsand is particularly useful in the manufacture of certain forms of electrical devices, it will hereinafter be set forth, for purposes of description, as directed to the manufacture of incandescent electric lamps of the vacuum type.

In the manufacture of incandescent electric lamps, there remains, after the evacuation of a bulb, a small amount of residual gas which it is not economical to withdraw. Further, after the completion of the manufacture of a lamp small amounts of gases or vapors are evolved from parts of the same when heated during operation. It is desirable to dispose of those vapors and gases in a manner which renders them harmless to the lamp.

Furthermore, on account of the high temperature at which the lamp is operated, portions of the filament vaporize and are condensed on the inner surface of the bulb, forming a dark colored deposit which decreases the amount of light emitted from the lamp. In order to maintain the candle power of'the. lamp it is highly desirable'to Various chemicals known as getters have been introduced into incandescent lamps for the purpose of eliminating deleterious gases and vapors and counteracting the obscuring effect of distilled filamentary material which condenses on the bulb of the lamp.

For obvious reasons these chemicals are introduced into the lamp in a comparatively fine state of sub-division, such as in granular form, and they are preferably disposed within the lamp in such a position that they Application filed May 18, 1921. Serial No. 470,672.

may be activated by the normal operation of the same. In practice, these chemicals or getters are preferably placed on the filament, or on the filament-supports of the lamp.

It is necessary to su 1 means for causi the anulated getter tb adhere to the ni teria to which it is applied, since the chemi cals which have been .found useful as getters are not-of an adhesive nature. It has heretofore been the practice to mix the comminuted getter with an adhesive binding agent to cause the getter to adhere to the parts of the lam to which it. was applied. The use 0 a binding agent, however, has by so much, complicated the manuv facture of incandescent electric lamps and ntroduced a material which was not in tself a etter and very frequently impaired the eificiency of lamps. Of the binding agents which have been used for these purposes, organic chemicals have been preferred as being as harmful to lamp parts than certain (inorganic binders which have been propose Nevertheless, many disadvantages and defacts-are inherent in organic binders. The objectionable roperites of an organic binder manifest. t emselves when such binders are decom osed by the heat which is used to activate t e getter material. The decomposition of the organic binder results in an evolution of electrically conducting gases which may cause the lam to become short circuited between the l ing-in wires, and

further leaves a residual amount of carbon which combines with the filament, if of ametallic nature, to form carbides which greatly impair the strength of the filamentary material. To eliminate the considerable quantity of gases evolved in the decomposition of the organic binder, it has been the practice heretofore, to introduce into a.

' (lacing l aeai nears-1g ea en i a; a yellow: as as: P in rea the an? 1 s a? ar a getter aitiio I gbedan hegette" .1 were negated later when Ethe' getter The i pres-em inveh tired seem-n1; affi' eliminating vt extraneous gases into a lamp, the present invention thereby removes the necessity of providing a substance such as phosphorus to combine with such gases. It has been found that the small amount of residual gases remaining in a lamp after exhaustion may be efficiently disposed of by the same material which is introduced to offset the obscuring effect of volatilized filamentary material.

Many kinds of material may be used as a getter and various modes of accomplishing the desired results may be contrived, but the following description of a method of applying my invention will be given only as a preferred form.

The present invention contemplates the reduction of the surface area of the pulverized getter, whereby the'adsorbed gas may be expelled from the same. This reduction of surface area leaves the getter in an optimum condition for minimum subsequent gaseous adsorption. As a method of expelling adsorbed gases the surface area is preferably reduced by fusing the getter. If the getter is fused to a lamp part means is thereby afforded for firmly affixing the getter to the lamp part.

The fusion of a getter into a mass of small surface contributes a further advanhe'se factors E which? I introduce 5 neaaeaa incanrlescen lampfj v sele'ss within a. very short periodof time, s apparent that; 5 :inethod :renderi I getter:non-hygroscopic is my in Jab jI h =uuder sensid P e r re :g be obscuring after. 5ntary= former; is conram a iithjeisbsc iri geli mentary material perunit area of bulb face is diminished.

The method of distilling the getter is a means for combiningwith, or otherwise removing, the small amount of residual gas, since it is known that the distillation of a materialin a vessel containing a small amount of gas adsorbs the gas while in the vaporized state and retains it when condensed; since the getter in the presentin stance is deposited on the comparatively 0001 surface of the lamp the adsorbed gas will not be re-evolved.

The getter material, according to the present invention, is preferably granulated and added to a liquid medium such as water to form either a solution or a suspension, which is preferably applied to the filamentary material before the latter is mounted on the stem of the lamp. The getter preparation may be applied by passing a heated filamentary material, -such as tungsten, through it. It is preferred to heat the wire While pass ing it through the getter preparation, as the heat serves to immediately dehydrate the preparation and to cause it to temporarily adhere to the filamentary material. 'The the fusion point of the getter. This process firmly affixes the getter to the filamentary material and at the same time expels the adsorbed gases and reduces the surface area so as to render it less adsorbent to gases.

The method of heating the wire by an electric current has been found to be very simple and eflicient and is the preferred mode of heating. In applying the getter it is not necessary to perform the operation in an inert atmosphere although the filamentary material is raised to oxidation tem-' perature, inasmuch as the wire is protected from the atmosphere by the coating of getter.

Ithas been found that the fused coatlng of getter strengthens a filamentary material, such as tungsten, so that the latter may be more readily handled without breaking. This additional strength is especially valuable in filament wire of very small diameter as s ch wire breaks ver readily. Similarly, the fused coating furt e'r facilitates the manipulation of such filamentary material by lending to it qualities which prevent the wire from tangling and kinking.

The filamentary material with its fused coating of getter is mounted within the lamp in the usual manner, and after the evacuation and sealing of the envelope, the lamp is lighted at its designed potential, without the necessity of auxiliary apparatus to guard against short circuits therein, inasmuch as there is not present a sufficient quantity of gases to permit gaseous conduction at lampvoltages.

The incandescent filament serves to vaporize the getter, which, in the vapor state,

combines with the small amount of residual gas either chemically or physically. and, reaching the comparatively cool surface of the bulb, is condensed on the bulb as an invisible deposit and there serves its function of adsorbing the ordinarily obscuring 'deposit of filamentary material, according to the theory stated above.

The double fluoride of sodium and aluminum, known as cryolite, is an instance of a getter which has been applied in the manner described and which functions as stated in the foregoing exposition. This material in granular form may be suspended in water in'any desired quantity, depending on the predetermined amount calculated as being necessary to maintain the candle power and increase the efiiciency of an incandescent lamp.

Experience has shown that wire gettered accordingto the presentinvention resists the ordinar abrasion which may occur in manufacturing manipulations, 'and maintains itself on the wire to the full quantity as applied. This is a distinct advantage inasmuch as the amount of getter applied is a predetermined quantity calculated as being the optimum for making the most efiL cient lamp.

The present invention is also valuable in the manufacture of vacuum or gas filled tubes which employ an electron-emitting element. Such elements of electron tubes may consist of an electrode coated with materials, such as oxides, which function as the major electron-emitting element. It is necessary that the electron emission from such coated electrodes be constant in quantity, which requires that the coating be maintained on the electrode. without loss therefrom. The method disclosed in the present invention of-firml afiixing such a coating to an electrode will therefore be valuable in the manufacture of electron tubes.

It will be appreciated from the foregoing that the present invention accomplishes the objects of the invention and that it is aconsiderable advance over the prior art.

It is to be understood that in appreciating this invention the scope thereof is not to be limited to the specific illustrations cited herein but is confined only by the scope of the invention as set forth in the appended claims.

What is claimed is:

1. The step in the manufacture of a vacuum electric device employing a filament which consists in fusing onto the filament of such a device, prior to incorporation of the filament into the device, a uniformly distributed layer of a vaporizable material whlch is beneficial to the operation of the same.

2. The method of affixing a powdered getter material to a filament which consists in suspending the getter material in a liquid, passing the filament through the suspension n a heated condition and subsequently fus mg the getter material onto the filament.

3. The method of uniting a getter substance in powder form to a filamentary substance which comprises heating one of sai substances in contact with the other to a suflicient degree so as to fuse the getter substance to the filamentary substance and allowing the getter to solidify thereon.

4. The method of affixing a getter free from a binder to a filamentary material, which consists in coating the filamentary material with a getter and heating said getter to a temperature suflicient to fuse the same to the filamentary material and allowing the getter to solidify thereon.

5. The method of affixing a cryolite getter free from a binder to a filamentary material, which consists in coating the filamentary material with cryolite, heating said cryolite to a temperature sufficient to expel absorbed ases therefrom and to cause said cryolite to fuse and adhere to the filamentary material and allowing the getter to solidify thereon.

6. The method of afiixing a getter free from a binder to a filamentary material, which consists in applying a coating of cryolite to tungsten wire, heating said wlre to a sufliciently high temperature to cause the cryolite to fuse and allowing the fused cryolite to solidify on the filamentary material. v

7. The-.method of facilitating the manipulation of a filament of small diameter, which consists -in fusing a coating of cryolite on.

the filament.

8. An electric device comprising an evacuated sealed envelope and a filament having a coating of'cryolite fused and solidified thereon. a

9. An incandescent electric lamp comprising an evacuated sealed envelope and a fila- .ment having thereon a fused and solidified Within' the lamp and to form a non-obscuring deposit with the distilled, portion of filamentary material in the envelope of said lamp.

In testimony whereof, I have hereunto subscribed my name this 17th day of May,

DUNCAN MAORAE. 

